Nikon D70SNikon updates its midrange SLR with improved focusing, larger LCD, a new menu interface, and more.<<Optics :(Previous) | (Next): Flash>> Page 8:ExposureReview First Posted: 06/30/2005 |
Exposure
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ISO sensitivity ranges from 200 to 1600, adjustable by pressing the ISO button and turning the Main command dial to change the setting on the Status LCD. It can also be changed in the menu. A Noise Reduction mode in the settings menu reduces fixed-pattern image noise when shooting at the higher sensitivity settings at longer exposure times. White balance modes include Auto, which covers almost the entire range from 3,500K to 8,000K. It can also be set manually for Incandescent (3,000K), Fluorescent (4,200K), Sunlight (5,200K), Flash (5,400K), Cloudy (6,000K), Shade (8,000K), or Preset, which the user sets based on a white or gray object in the scene or a pre-captured photograph. My biggest gripe is that neither Auto nor Incandescent reach down far enough to handle the household incandescent lighting that's so common in the US. (Although Incandescent can be tweaked enough to almost get there.) Why can't digicam companies make auto white balance options with enough range to cover this very common light source?
White balance can be fine tuned by pressing the WB button and turning the sub-command dial. It can be adjusted from -3 to +3 in increments of 1, but the actual step size varies as a function of the white balance mode that's selected. See table below for details, which shows the lighting color temperature that each setting corresponds to.
| Camera Display--> | -3 | -2 | -1 | 0 | 1 | 2 | 3 |
| Direct Sunlight | 5600 | 5400 | 5300 | 5200 | 5000 | 4900 | 4800 |
| Shade | 9200 | 8800 | 8400 | 8000 | 7500 | 7100 | 6700 |
| Overcast | 6600 | 6400 | 6200 | 6000 | 5800 | 5600 | 5400 |
| Incandescent | 3300 | 3200 | 3100 | 3000 | 2900 | 2800 | 2700 |
| Fluorescent | 7200 | 6500 | 5000 | 4200 | 3700 | 3000 | 2700 |
| Flash | 6000 | 5800 | 5600 | 5400 | 5200 | 5000 | 4800 |
The D70S has three metering options, 3D Matrix, Center Weighted, and Spot. The 3D Matrix setting integrates exposure information from 1,005 areas across the entire screen, as opposed to most multisegment sensors that have from 10 to 35 areas to analyze. The scene viewed by the metering sensor is compared to a database of common photographic situations to help the camera decide whether the image consists of a backlit subject, for example, or else a dark foreground object. This information is enhanced (essentially made "3D") by the focus distance information shared from the microchip in the D- and G-series lenses. The net result of all this is a more frequently accurate metering response than that produced by center weighted metering, especially if the subject is off-center. In practice, I found the D70S' metering to generally be quite accurate. It seemed to have a tendency to slightly underexpose most shots by about 0.3 EV, but it was pretty consistent in this, leading me to believe that this might represent a deliberate choice by its designers, to avoid losing highlight detail. (The D70 had a similar tendency, but my sense is that the amount of underexposure is slightly less with the D70S.) Overall, I felt pretty confident of getting the exposure I expected with the D70S, after relatively little time spent with the camera.
As to the other metering options for the D70S, center-weighted metering takes a light reading from the entire image area, but places the greatest emphasis on a circular area in the center. In an unusual feature for an "entry level" d-SLR, as Custom Function menu option lets you select how large an area contributes toward the center-weighting. Options are 6, 8, 10, and 12 mm, with 8mm being the default (and the only area actually indicated in the viewfinder). Spot metering in the D70S takes a reading centered on the active focus area (about one percent of the frame), excellent for quick measurements from a face without having to close the distance much.
The D70S' Exposure compensation adjustment lightens or darkens the overall exposure anywhere from -5 to +5 EV units, in one-third step increments. It can also be adjusted to work in half step increments. Note though, that exposure compensation does not work in the Auto mode or any of the Digital Vari-Program modes. As noted above, I found the D70S to fairly consistently underexpose shots by about 0.3 EV, since most of my shots were better when I boosted the exposure compensation by that amount. By default, test shots captured under harsh lighting showed the D70S to be quite a bit more contrasty than I'd personally prefer, although the color from the D70S is excellent. There is a variable contrast control buried in the shooting menu that lets you adjust the contrast level to low, normal, or high. I found that this worked reasonably well, but didn't have as much of an effect when used to decrease the contrast as it did when increasing it. Overall, I'd really like to see more capability to reduce the camera's somewhat high native contrast than is provided.
An auto-bracketing feature takes three shots of the same subject with varying exposure values determined by either the photographer in manual mode or by the camera in all other modes. The exposure steps for bracketing can vary across a range of -2 to +2 EV (values are added to the already chosen exposure compensation value), in increments of either one-third or one-half. Through the Custom Settings menu, the Bracketing function can also be set to bracket exposure and flash-level, flash exposure only, or white balance only. (By default, both ambient and flash exposures are bracketed.)
The D70S also offers Hue, Sharpness, Tone Compensation (Contrast), and Saturation adjustments, accessed through the Shooting menu. I mentioned the contrast adjustment feature above, but its Custom option deserves special mention. What's unusual here (for an entry-level d-SLR at least) is that the Custom tone compensation option accepts downloaded tone curves from a computer. (If no curve is downloaded, the Custom setting defaults to the Normal setting.) This lets you completely define the camera's tonal characteristics via the computer, something that has heretofore only been available on the highest-end d-SLR models.
For those familiar with the concept of the "color wheel", which arranges visible colors in a circle, Nikon's Hue adjustment will make sense: It offers a range of adjustment from -9 to +9 degrees around the color wheel. (A complete circuit of the wheel being 360 degrees.) If you don't carry a degree-calibrated color wheel in your head, I've provided the illustration of a color wheel at right. The dark bars show the total shift that the full 18 degree range of adjustment offered by the D70S' hue control can produce. - As you can see, it's a fairly subtle adjustment. Note too, that the effect on any given color will depend on where that color is around the wheel. For red colors, a positive adjustment will shift the red toward orange, while a negative adjustment will shift it toward purple. For blues though, positive adjustments shift the color toward purple, while negative adjustments shift it toward cyan. The rollover image below shows the effect of going from -9 to +9 on the Hue adjustment - The -9 shot is visible by default, move your cursor over the image to see the effect of the shift to +9 degrees.
When reviewing images on the LCD monitor, you can call up a histogram and a highlight function to give you a complete readout on the exposure. This is a useful tool to examine your exposure in the camera instead of waiting to download images and then deciding to reshoot. As I noted in my discussion of these features in the Viewfinder section of this review, I'd like to see the Highlight function be a little more restrained in its reporting of overly-strong highlights. (Actually, the ideal would be to let the user select at what brightness level the highlight warning should activate. Why hasn't any manufacturer done this yet?)
Continuous Shooting Mode
Nikon claims that the D70S' Continuous Shooting mode captures 3 frames per second, depending on the amount of image information and available Compact Flash space. In practice, I clocked it at 3.05 fps, quite close. When using a fast Compact Flash card, like a Lexar 80x, or SanDisk's Ultra II, Extreme or Extreme III, the buffer doesn't fill very quickly. The buffer-frames-remaining counter decreases slowly but steadily in large/fine JPEG mode, very slowly in large/normal mode, and not at all at the large/basic quality setting. The faster the card, the more quickly the buffer can offload the data, and in the case of high resolution with "normal" or "basic" compression, the buffer may never fill at all. This is truly amazing, the original D70 was the first digital camera I saw that could do this. Do note though, that this effect requires a card write speed rating of 9MB/second or more. (Finally, a camera that really takes advantage of fast memory cards!)
Image Noise
Overall, the D70 has pretty good noise characteristics. The chart below shows a plot of noise magnitude vs ISO value for the D70S and several competing models, but as usual, the chart tells only a small portion of the story. While the D70S shows numerically higher noise levels, particularly at very high ISO settings, in actual fact, the noise pattern of the D70 is pretty finer-grained. This makes it less objectionable to the eye. Bottom line, I found the D70S's images shot at ISO 1600 to be quite acceptable for all but the most critical applications. For routine shooting of family memories, I have no qualms about running the D70S at its maximum ISO setting on a routine basis.
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